Cooled grommet for a combustor wall assembly

ABSTRACT

A combustor wall assembly has a heat shield and a supporting shell with a cooling cavity defined therebetween. A grommet generally includes a wall defining a dilution hole isolated from the cooling cavity, and a flange projecting radially outward from the wall and into the cooling cavity. The flange is space from the heat shield and a cooling channel is defined between the wall and the heat shield that communicates with the cavity for cooling the wall proximate to a combustion chamber.

This application claims priority to PCT patent application Ser. No.PCT/US14/072,358 filed Dec. 24, 2014 which claims priority to U.S.Patent Application No. 61/923,469 filed Jan. 3, 2014, which are herebyincorporated herein by reference in their entireties.

BACKGROUND

The present disclosure relates to a gas turbine engine and, moreparticularly, to a grommet for a combustor wall assembly.

Gas turbine engines, such as those that power modern commercial andmilitary aircraft, include a fan section to propel the aircraft, acompressor section to pressurize a supply of air from the fan section, acombustor section to burn a hydrocarbon fuel in the presence of thepressurized air, and a turbine section to extract energy from theresultant combustion gases and generate thrust.

The combustor section typically includes a wall assembly having an outershell lined with heat shields that are often referred to as floatwallpanels. Together, the panels define a combustion chamber. A plurality ofdilution holes are generally spaced circumferentially about the wallassembly and flow dilution air from a cooling plenum and into thecombustion chamber to improve emissions, and reduce and control thetemperature profile of combustion gases at the combustor outlet toprotect the turbine section from overheating.

The dilution holes are generally defined by a grommet that extendsbetween a heat shield panel and supporting shell with a cooling cavitydefined therebetween. Enhanced cooling of the grommets is desirable forimproved robustness and durability.

SUMMARY

A grommet according to one, non-limiting, embodiment of the presentdisclosure includes a first wall defining a dilution hole disposed alonga centerline, a first flange projecting outward from the first wall andincluding a first face and an opposite second face, and a plurality ofstandoffs engaged to the first face.

Additionally to the foregoing embodiment, the first wall includes firstand second portions projecting outward from the respective first andsecond faces, and the plurality of standoffs are spaced radially outwardfrom the first portion.

In the alternative or additionally thereto, in the foregoing embodimentthe plurality of standoffs are spaced circumferentially fromone-another.

In the alternative or additionally thereto, in the foregoing embodimentthe plurality of standoffs project outward from the first face and arean integral and unitary part of the first flange.

In the alternative or additionally thereto, in the foregoing embodimentthe plurality of standoffs are brazed to the first face.

In the alternative or additionally thereto, in the foregoing embodimentthe grommet includes a second flange spaced radially outward from thefirst portion and spaced axially from the first face, wherein each oneof the plurality of standoffs spans between the first face and thesecond flange.

In the alternative or additionally thereto, in the foregoing embodimenteach one of the plurality of standoffs is engaged to the second flange.

In the alternative or additionally thereto, in the foregoing embodimentthe grommet includes a second wall spaced radially outward from andconcentric to the first portion and spaced axially from the first face.

In the alternative or additionally thereto, in the foregoing embodimentthe first portion and the second wall define an annular cooling channeltherebetween.

In the alternative or additionally thereto, in the foregoing embodimentthe first portion includes an annular first face, and the second wallincludes an annular second face disposed substantially flush with theannular first face.

A combustor wall assembly according to another, non-limiting, embodimentof the present disclosure includes a heat shield, a shell, and agrommet, wherein the heat shield and the shell at least partially definea cooling cavity therebetween, and the grommet defines a dilution holecommunicating through the heat shield and the shell isolated from thecooling cavity and a cooling channel in communication with the coolingcavity.

Additionally to the foregoing embodiment, the grommet includes a firstwall defining at least in-part the dilution hole and a first flangeprojecting outward from the first wall and into the cooling cavity.

In the alternative or additionally thereto, in the foregoing embodiment,the heat shield includes a first surface defining a first aperturecommunicating through the heat shield, and the first wall projectsaxially from the first flange and into the first aperture and is spacedradially inward from the first surface.

In the alternative or additionally thereto, in the foregoing embodiment,the shell includes a second surface defining a second aperturecommunicating through the shell and centered to the centerline, and thefirst wall projects axially from the flange and into the secondaperture.

In the alternative or additionally thereto, in the foregoing embodimentthe first wall is radially spaced from the second surface.

In the alternative or additionally thereto, in the foregoing embodiment,the first flange includes a first face facing and spaced from the heatshield, and an opposite second face in contact with the shell.

In the alternative or additionally thereto, in the foregoing embodiment,a plurality of standoffs are spaced circumferentially from one-another,span between the first flange and the heat shield, and are spacedradially outward from the first wall.

In the alternative or additionally thereto, in the foregoing embodimenta second flange is spaced radially outward from the first wall andspaced axially from the first flange, and the plurality of standoffsspan between the first and the second flanges.

In the alternative or additionally thereto, in the foregoing embodiment,the first flange is in sealing contact with the shell and the secondflange is in contact with the heat shield.

In the alternative or additionally thereto, in the foregoing embodimenta second wall projects axially from the second flange and into the firstaperture, and the second wall is spaced radially outward from the firstwall and spaced axially from the first flange.

In the alternative or additionally thereto, in the foregoing embodiment,the plurality of standoffs are an integral and unitary part of the heatshield and are brazed to the first flange.

The foregoing features and elements may be combined in variouscombination without exclusivity, unless expressly indicated otherwise.These features and elements as well as the operation thereof will becomemore apparent in light of the following description and the accompanyingdrawings. It should be understood, however, the following descriptionand figures are intended to exemplary in nature and non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features will become apparent to those skilled in the art fromthe following detailed description of the disclosed non-limitingembodiments. The drawings that accompany the detailed description can bebriefly described as follows:

FIG. 1 is a schematic cross-section of a gas turbine engine;

FIG. 2 is a cross-section of a combustor section;

FIG. 3 is a partial cross section of a combustor wall assembly having agrommet according to one non-limiting example of the disclosure;

FIG. 4 is a top plan view of the grommet;

FIG. 5 is a plan view of a cold side of a heat shield of the wallassembly;

FIG. 6 is a cross section of a second non-limiting example of a wallassembly having a grommet; and

FIG. 7 is a cross section of the wall assembly taken along line 7-7 ofFIG. 6.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a gas turbine engine 20 disclosed as atwo-spool turbo fan that generally incorporates a fan section 22, acompressor section 24, a combustor section 26 and a turbine section 28.Alternative engines may include an augmentor section (not shown) amongother systems or features. The fan section 22 drives air along a bypassflowpath while the compressor section 24 drives air along a coreflowpath for compression and communication into the combustor section 26then expansion through the turbine section 28. Although depicted as aturbofan in the disclosed non-limiting embodiment, it should beunderstood that the concepts described herein are not limited to usewith turbofans as the teachings may be applied to other types of turbineengine architecture such as turbojets, turboshafts, and three-spoolturbofans with an intermediate spool.

The engine 20 generally includes a low spool 30 and a high spool 32mounted for rotation about an engine axis A via several bearingstructures 38 and relative to a static engine case 36. The low spool 30generally includes an inner shaft 40 that interconnects a fan 42 of thefan section 22, a low pressure compressor 44 (“LPC”) of the compressorsection 24 and a low pressure turbine 46 (“LPT”) of the turbine section28. The inner shaft 40 drives the fan 42 directly or through a gearedarchitecture 48 to drive the fan 42 at a lower speed than the low spool30. An exemplary reduction transmission is an epicyclic transmission,namely a planetary or star gear system.

The high spool 32 includes an outer shaft 50 that interconnects a highpressure compressor 52 (“HPC”) of the compressor section 24 and a highpressure turbine 54 (“HPT”) of the turbine section 28. A combustor 56 ofthe combustor section 26 is arranged between the HPC 52 and the HPT 54.The inner shaft 40 and the outer shaft 50 are concentric and rotateabout the engine axis A. Core airflow is compressed by the LPC 44 thenthe HPC 52, mixed with the fuel and burned in the combustor 56, thenexpanded over the HPT 54 and the LPT 46. The LPT 46 and HPT 54rotationally drive the respective low spool 30 and high spool 32 inresponse to the expansion.

In one non-limiting example, the gas turbine engine 20 is a high-bypassgeared aircraft engine. In a further example, the gas turbine engine 20bypass ratio is greater than about six (6:1). The geared architecture 48can include an epicyclic gear train, such as a planetary gear system orother gear system. The example epicyclic gear train has a gear reductionratio of greater than about 2.3:1, and in another example is greaterthan about 2.5:1. The geared turbofan enables operation of the low spool30 at higher speeds that can increase the operational efficiency of theLPC 44 and LPT 46 and render increased pressure in a fewer number ofstages.

A pressure ratio associated with the LPT 46 is pressure measured priorto the inlet of the LPT 46 as related to the pressure at the outlet ofthe LPT 46 prior to an exhaust nozzle of the gas turbine engine 20. Inone non-limiting example, the bypass ratio of the gas turbine engine 20is greater than about ten (10:1); the fan diameter is significantlylarger than the LPC 44; and the LPT 46 has a pressure ratio that isgreater than about five (5:1). It should be understood; however, thatthe above parameters are only exemplary of one example of a gearedarchitecture engine and that the present disclosure is applicable toother gas turbine engines including direct drive turbofans.

In one non-limiting example, a significant amount of thrust is providedby the bypass flow path B due to the high bypass ratio. The fan section22 of the gas turbine engine 20 is designed for a particular flightcondition—typically cruise at about 0.8 Mach and about 35,000 feet. Thisflight condition, with the gas turbine engine 20 at its best fuelconsumption, is also known as bucket cruise Thrust Specific Fuelconsumption (TSFC). TSFC is an industry standard parameter of fuelconsumption per unit of thrust.

Fan Pressure Ratio is the pressure ratio across a blade of the fansection 22 without the use of a fan exit guide vane system. The low FanPressure Ratio according to one non-limiting example of the gas turbineengine 20 is less than 1.45:1. Low Corrected Fan Tip Speed is the actualfan tip speed divided by an industry standard temperature correction of(T/518.7^(0.5)), where “T” represents the ambient temperature in degreesRankine. The Low Corrected Fan Tip Speed according to one non-limitingexample of the gas turbine engine 20 is less than about 1150 fps (351m/s).

Referring to FIG. 2, the combustor section 26 generally includes anannular combustor 56 with an outer combustor wall assembly 60, an innercombustor wall assembly 62, and a diffuser case module 64 that surroundsassemblies 60, 62. The outer and inner combustor wall assemblies 60, 62are generally cylindrical and radially spaced apart such that an annularcombustion chamber 66 is defined therebetween. The outer combustor wallassembly 60 is spaced radially inward from an outer diffuser case 68 ofthe diffuser case module 64 to define an outer annular plenum 70. Theinner wall assembly 62 is spaced radially outward from an inner diffusercase 72 of the diffuser case module 64 to define, in-part, an innerannular plenum 74. Although a particular combustor is illustrated, itshould be understood that other combustor types with various combustorliner arrangements will also benefit. It is further understood that thedisclosed cooling flow paths are but an illustrated embodiment andshould not be so limited.

The combustion chamber 66 contains the combustion products that flowaxially toward the turbine section 28. Each combustor wall assembly 60,62 generally includes a respective support shell 76, 78 that supportsone or more heat shields or liners 80, 82. Each of the liners 80, 82 maybe formed of a plurality of floating panels that are generallyrectilinear and manufactured of, for example, a nickel based super alloythat may be coated with a ceramic or other temperature resistantmaterial, and are arranged to form a liner configuration mounted to therespective shells 76, 78.

The combustor 56 further includes a forward assembly 84 that receivescompressed airflow from the compressor section 24 located immediatelyupstream. The forward assembly 84 generally includes an annular hood 86,a bulkhead assembly 88, and a plurality of swirlers 90 (one shown). Eachof the swirlers 90 are circumferentially aligned with one of a pluralityof fuel nozzles 92 (one shown) and a respective hood port 94 to projectthrough the bulkhead assembly 88. The bulkhead assembly 88 includes abulkhead support shell 96 secured to the combustor wall assemblies 60,62 and a plurality of circumferentially distributed bulkhead heatshields or panels 98 secured to the bulkhead support shell 96 aroundeach respective swirler 90 opening. The bulkhead support shell 96 isgenerally annular and the plurality of circumferentially distributedbulkhead panels 98 are segmented, typically one to each fuel nozzle 92and swirler 90.

The annular hood 86 extends radially between, and is secured to, theforwardmost ends of the combustor wall assemblies 60, 62. Each one ofthe plurality of circumferentially distributed hood ports 94 receives arespective on the plurality of fuel nozzles 92, and facilitates thedirection of compressed air into the forward end of the combustionchamber 66 through a swirler opening 100. Each fuel nozzle 92 may besecured to the diffuser case module 64 and projects through one of thehood ports 94 into the respective swirler 90.

The forward assembly 84 introduces core combustion air into the forwardsection of the combustion chamber 66 while the remainder of compressorair enters the outer annular plenum 70 and the inner annular plenum 74.The plurality of fuel nozzles 92 and adjacent structure generate ablended fuel-air mixture that supports stable combustion in thecombustion chamber 66.

Referring to FIGS. 3 through 5, a grommet 102 is illustrated and furtherdescribed in relation to the outer wall assembly 60 for simplicity ofexplanation; however, it is understood that the same grommet may beapplied to the inner wall assembly 62 of the combustor 56. The heatshield 80 of wall assembly 60, which may include an array of panels,carries a hot side 104 that generally defines in-part a boundary of thecombustion chamber 66 and an opposite cold side 106. The shell 76carries an outer side 108 that faces and defines in-part a boundary ofthe cooling plenum 70 and an opposite inner side 110 that faces the coldside 106 of the heat shield 80. An annular cooling cavity 112 is locatedbetween and defined by the cold side 106 of the heat shield 80 and theinner side 110 of the shell 76.

An aperture 114 communicates through the heat shield 80 and is definedby a continuous surface 116 carried by the heat shield 80 and spanningbetween the hot and cold sides 104, 106. Similarly, an aperture 118communicates through the shell 76 and is defined by a continuous surface120 carried by the shell 76 and spanning between the outer and innersides 108, 110. A centerline 122 extends through the apertures 114, 118and may be substantially normal to the wall assembly 60 and mayintersect the engine axis A.

The grommet 102 has a continuous or cylindrical wall 124 that defines adilution hole 126, and a flange 128 that projects radially outward (withrespect to the centerline 122) from the wall 124 and into the coolingcavity 112. The flange 128 carries inner and outer faces 130, 132 suchthat an outer portion 134 of the wall 124 generally projects axiallyoutward from the outer face 130 (with respect to centerline 122) andthrough the aperture 118 of the shell 76, and an inner portion 136 ofthe wall 124 generally projects axially inward from the inner face 130and into the aperture 114 in the heat shield 80.

When assembled, the inner face 130 of the flange 128 may be spaced fromthe cold side 106 of the heat shield 80 by a plurality of standoffs 138of the grommet 102 (three illustrated as an example). The standoffs 138are circumferentially spaced from one another about the aperture 114 ofthe heat shield 80 and span between the inner face 130 of the flange 128and the cold side 106 of the heat shield 80. Each standoff 138 may be anintegral and unitary part of the heat shield 80 with distal ends beingbrazed or otherwise secured to the inner face 130 of the flange 128. Theinner portion 136 of the wall 124 in the aperture 114 is spaced from thesurface 116 of the heat shield 80, such that a cooling channel 140,which may be annular in flow cross section, is defined between thesurface 116 and inner portion 136.

It is further understood and contemplated that the standoffs 138 mayalternatively, or in combination, project from the inner face 130 of theflange 128 and may be brazed to the cold side 106 of heat shield 80. Itis further understood that the heat shield 80 and grommet 102 may beformed as one unitary part through any number of manufacturing processessuch as processes utilizing leach-out cores, ceramic or Refractory MetalCore (RMC), or additive manufacturing.

The outer face 132 of the flange 128 may be in sealable and releasablecontact with the inner side 110 of the shell 76 and the outer portion134 of the wall 124 may be spaced radially from the surface 118 of theshell 76 to allow for thermal expansion during operation. The sealbetween the shell 76 and flange 128 helps to maintain the coolingintegrity and pressure differentials across the shell and heat shield80. Although not illustrated, the cooling cavity receives cooling airfrom the cooling plenum 70 and through a number of impingement holes inthe shell. From the cooling cavity 112, cooling air then flows through aplurality of strategically placed effusion holes in the heat shield 80with a combined flow that forms a cooling blanket across the hot side104 of the heat shield for thermal protection.

It is further contemplated and understood that while the grommet 102 maybe brazed to the wall assembly 60, it may instead be a separate partthat is held in place and indexed between the shell 76 and heat shield80. Such an arrangement may simplify maintenance and enable grommetsmade of differing or more expensive material that better resistoxidation than, for example, the heat shield 80. In such an arrangement,the sealing contact between the flange 128 and the shell 76 and thecontact between the standoffs 138 and the flange 128 act to index andhold the grommet axially with respect to the wall assembly 60. Radialindexing, required to maintain radial clearances for the annular coolingchannel 140, can be accomplished by including recesses in the inner face130 of flange 128 that respectively receive the standoffs 138. It isfurther understood and contemplated that other indexing means may beapplied than that illustrated or described.

In operation, dilution air flows from the plenum 70, through thedilution hole 126 and into the combustion chamber 66 as signified byarrow 139. Cooling air flows from the cooling cavity 112, between theflange 128 and cold side 106 of heat shield 80 (thus about the standoffs138), then through the annular cooling channel 140 and into thecombustion chamber 66 as signified by arrow 141. The cooling air bathsand cools the inner portion 136 of the wall 124 most exposed to the hotgases in the combustion chamber 66 and the dilution air enters thecombustion chamber in a much higher volume and generally as a jet streamto cool the combustion gases in a core region of the chamber.

Referring to FIGS. 6-7, a second example of a grommet is illustratedwherein like components to the first example have like identifyingelement numbers except with the addition of a prime symbol. The grommet102′ further has a second flange 142 that carries an annular inner face144 and an opposite annular outer face 146. The outer face 146 of thesecond flange 142 is axially spaced from an inner face 130′ of a firstflange 128′ by a plurality of standoffs 138′. The grommet 102′ may becast as one piece such that the standoffs 128′ are formed to theopposing faces 146, 130′. The inner face 144 of the second flange 142may be brazed to the cold side 106′ of a heat shield 80′.

The grommet 102′ further has an outer wall 148 that may be substantiallycylindrical and projects axially from an inner periphery of the secondflange 142 and into an aperture 114′ in the heat shield 80′. The outerwall 148 carries a radial inner surface 150 and an opposite radial outersurface 152. An annular cooling channel 140′ is defined between a wallportion 136′ of an inner wall 124′ and the inner surface 150 of theouter wall 148. The outer surface 152 of the outer wall 148 opposes andmay be in contact with a continuous surface 116′ of the heat shield 80′that defines the aperture 114′. Both the outer wall 148 and the wallportion 136′ of the inner wall 124′ have respective annular faces 154,156 at distal ends that may be substantially flush with one-another, andmay be substantially flush with a hot side 104′ of the heat shield 80′.

It is understood that relative positional terms such as “forward,”“aft,” “upper,” “lower,” “above,” “below,” and the like are withreference to the normal operational attitude and should not beconsidered otherwise limiting. It is also understood that like referencenumerals identify corresponding or similar elements throughout theseveral drawings. It should be understood that although a particularcomponent arrangement is disclosed in the illustrated embodiment, otherarrangements will also benefit. Although particular step sequences maybe shown, described, and claimed, it is understood that steps may beperformed in any order, separated or combined unless otherwise indicatedand will still benefit from the present disclosure.

The foregoing description is exemplary rather than defined by thelimitations described. Various non-limiting embodiments are disclosed;however, one of ordinary skill in the art would recognize that variousmodifications and variations in light of the above teachings will fallwithin the scope of the appended claims. It is therefore understood thatwithin the scope of the appended claims, the disclosure may be practicedother than as specifically described. For this reason, the appendedclaims should be studied to determine true scope and content.

What is claimed is:
 1. A grommet for a combustor of a gas turbinecomprising: a first wall defining a dilution hole of the combustordisposed along a centerline; a first flange projecting outward from thefirst wall and including a first face and an opposite second face; and aplurality of standoffs extending from the first face; wherein the firstwall includes first and second portions projecting outward from therespective first and second faces, wherein a second flange spacedradially outward from the first portion and spaced axially from thefirst face forms a cooling channel therebetween, and wherein each one ofthe plurality of standoffs spans between the first face and the secondflange.
 2. The grommet set forth in claim 1, wherein the plurality ofstandoffs are spaced radially outward from the first portion.
 3. Thegrommet set forth in claim 2, wherein the plurality of standoffs arespaced circumferentially from one-another.
 4. The grommet set forth inclaim 3, wherein the plurality of standoffs project outward from thefirst face and are an integral and unitary part of the first flange. 5.The grommet set forth in claim 1, wherein each one of the plurality ofstandoffs is engaged to the second flange.
 6. The grommet set forth inclaim 5, further comprising: a second wall spaced radially outward fromand concentric to the first portion and spaced axially from the firstface.
 7. The grommet set forth in claim 6, wherein the first portion andthe second wall define the cooling channel therebetween, and the coolingchannel comprises an annular cooling channel.
 8. The grommet set forthin claim 6, wherein the first portion includes an annular first face,and the second wall includes an annular second face disposedsubstantially flush with the annular first face.
 9. A combustor wallassembly, comprising: a heat shield; a shell; and a grommet; wherein theheat shield and the shell at least partially define a cooling cavitytherebetween; and wherein the grommet defines: a first wall defining atleast in-part a dilution hole about a centerline that communicatesthrough the heat shield and the shell, and is isolated from the coolingcavity; a first flange projecting radially outward from the first walland into the cooling cavity; a second flange spaced radially outwardfrom the first wall and spaced axially from the first flange to define acooling channel in communication with the cooling cavity; and aplurality of standoffs that span between the first flange and the secondflange.
 10. The combustor wall assembly set forth in claim 9, whereinthe heat shield includes a first surface defining a first aperturecommunicating through the heat shield, and the first wall projectsaxially from the first flange and into the first aperture and is spacedradially inward from the first surface.
 11. The combustor wall assemblyset forth in claim 10, wherein the shell includes a second surfacedefining a second aperture communicating through the shell and centeredto the centerline, and the first wall projects axially from the firstflange and into the second aperture.
 12. The combustor wall assembly setforth in claim 11, wherein the first wall is radially spaced from thesecond surface.
 13. The combustor wall assembly set forth in claim 9,wherein the first flange is in sealing contact with the shell and thesecond flange is in contact with the heat shield.
 14. The combustor wallassembly set forth in claim 9, further comprising: a second wallprojecting axially from the second flange and into the first aperture;and wherein the second wall is spaced radially outward from the firstwall and spaced axially from the first flange.